Why do leftovers taste better?

Why do leftovers often taste different (usually better) the day after than it did when it was hot? New Scientist:

Cooking or cooling changes various substances in foods, affecting composition and flavour. Yesterday’s leftovers have undergone reactions, including oxidation and the evaporation of aromas and flavour components. Food also changes physically on cooling, by congealing, crisping or crystallising, for example. These changes may prevent some substances from reaching the nose or the tongue, or expel or redistribute fluids. Few such changes reverse precisely on reheating, just as one cannot uncook food by chilling it.